1. Field of the Invention
This invention relates to alkylated biphenylyl phenyl ether sulfonates (A-BIPPE-S) and their use in enhanced oil recovery processes.
2. Background of the Invention
Most of the oil held in subterranean, porous rock reservoirs is produced, i.e., raised to the surface, either through the action of dissolved gases which force the oil to the surface as a froth or through a pumping action when natural reservoir pressure has been dissipated. These two production methods are termed primary oil recovery. However, such production methods usually recover less than about 25 percent of the known reservoir oil content.
Early in the 1900's, forcing water down selected well bores or injection wells to force oil through the reservoir pores to designated producing wells was accomplished successfully in Pennsylvania. Water flooding, or secondary oil recovery, has now been widely applied and presently accounts for more than half of the oil produced in the United States. This method usually adds about 15 percent to the total oil recovery from a given reservoir before the ratio of water:oil produced becomes so high (about 30:1) that the wells can no longer be operated economically.
Other methods used to recover the remaining portion (50-60 percent) of the original oil content of a reservoir are generally termed tertiary oil recovery or enhanced oil recovery methods. A variety of such methods are known and include steam flooding, miscible flooding with carbon dioxide, in situ combustion of part of the reservoir oil content, and flooding with micellar or aqueous surfactant solutions.
With regards to surfactant flooding, aqueous anionic surfactant systems are known to be useful for displacing oil from porous, subterranean rock reservoirs. These surfactant systems are generally comprised of petroleum sulfonates, often in combination with such materials as electrolytes, water-thickeners, and emulsion modifiers. While these systems demonstrate generally good efficiency, their utility is often limited by their low tolerance to multivalent cations. These cations, such as calcium and magnesium, are often encountered in brines of subterranean reservoirs and tend to form anionic surfactant precipitates or cause surfactant phase separations when contacted with aqueous anionic surfactant systems. Although the use of various cosurfactants, such as alkoxy-alcohol sulfates and aromatic ether polysulfonates, are known to improve the multivalent cation tolerance of these aqueous anionic surfactant systems, there continues a search for new such cosurfactants. Aqueous anionic surfactant systems, their tolerance problems to multivalent cations, and suggested cosurfactants for overcoming these tolerance problems are further described in U.S. Pat. No. 3,945,437, incorporated herein by reference, and the references cited therein.